So mate, per your argument, the green line is the breather line to crankcase, entering at "US driver" side cover, and the PCV on "US Psngr side" goes to manifold. That could be, (then I must have mexed where the joint goes, I'll check em tomorrow morning if weather helps
On the G8 V6 the Fresh Air Supply Line (green) runs from the intake tube in front of the throttle blade to the crankcase, entry point to crankcase is on USA drivers side valve cover at the rear.
On the G8 V6 the stale oily air (red) comes out of the rear of the USA passenger side valve cover where the PCV orifice (restrictor) is located.
On the G8 V8 the Fresh Air Supply line (green) runs to the USA passengers side valve cover at the front.
On the G8 V8 the stale oily air (red) comes out of the rear of the USA drivers side valve cover where the PCV orifice (restrictor) is located.
Stale oily air always runs to the intake manifold.
BUT how come the catch can I mounted on the green line traps things?
Read the GM Service Manual description above. During abnormal conditions there will be "backflow".
I'd imagine coming hard off the throttle could be one "abnormal condition" where you'd have more pressure inside the crankcase than in the air intake tube in front of the closed throttle blade. You're trapping things with your current install only when there's a backflow or reversion of the normal fresh air flow direction.
Disconnect both your current lines from your catchcan and have someone rev the engine up and down while you hold a finger over the end of both your lines, you'll soon tell from slight suction or slight pressure on your finger which way the air flow is during various conditions.